1. Field of the Invention
This invention relates to polyvinylpyrrolidone-hydrogen iodide-iodine (PVP-HI-I.sub.2) complexes, and to a process for making such complexes.
2. Description of the Prior Art
PVP-iodine has been used extensively in hospitals and elsewhere because of its germicidal, bactericidal, fungicidal and generally disinfecting properties. Usually it is sold as a brown powder, which contains about 10% available, or active iodine, and about 5% inactive iodine, in the form of iodide ion. The iodide ion is formed by reduction of iodine during preparation of the complex.
The partition coefficient of the complex, determined between an aqueous PVP-iodine solution and heptane, is a measure of the extent of bonding of iodine within the complex. A high partition coefficient value indicates a highly complexed iodine and little free iodine. Generally, known PVP-iodine complexes have partition coefficients of about 180 to 200. In complexes having a low partition coefficient, an iodine odor is perceptible from the complex and a moist potassium iodide starch paper introduced into the gas space above the PVP-iodine acquires a color, indicative of free iodine. Furthermore, aqueous solutions of PVP-iodine having a low partition coefficient are not very stable, i.e. they lose some available iodine upon storage.
Processes for making PVP-iodine complexes are disclosed in the following U.S. Pat. Nos.: 2,706,701; 2,739,922; 2,826,532; 2,900,305; 2,914,516; 3,028,300; 3,898,326; 4,027,083; 4,058,655; 4,094,967; 4,128,633; 4,200,710; 4,271,149; and 4,402,937. These prior art processes, however, are deficient in one or more respects, including poor complexation of iodine to PVP, and/or the requirement for excessive heating of the reactant components of the complex at elevated temperatures.
Accordingly, it is an object of the present invention to provide PVP-HI-I.sub.2 complexes in which the iodine is very strongly bound, as evidenced by a partition coefficient which is above 300, and, preferably of 350 or more.
Another object is to provide a process for making PVP-HI-I.sub.2 complexes having such exceptionally high partition coefficients, which process does not require extensive heating at elevated temperatures, and by which the complex is provided as a fine powder of light coloration.
These and other objects and features of the invention will be made apparent from the following more particular description of the ivnention.